Underarm/ Armpit Lump

A week ago I noticed a small lump about the size of a grain of rice under my arm at the top of my arm pit. It does not hurt, and hasn't appeared to have grown in the last week of noticing it, however there is a strong history of breast cancer in my family.
I am a 24 year old, with two children. My first son (5 years old) was breast fed for 4 months, my second son is only 8 weeks old, and i am currently breast feeding him.
My great grandmother had breast cancer, and my Sister who is only 28years old has just gone into remission from breast cancer, hers was hormonal though- not from her heritage. She has had a double macectomy and chemo for about 18 months. In the last month my great Aunt (my grandmothers sister) has been diagnosed with breast cancer, she is only 61 years old.
I am only 24 years old myself, but with 3 breast cancer cases being so close to home, I was wondering if such a lump is cause for worry.

You have a strong family history of breast cancer, especially your sister who got it at age 28.
You are breastfeeding your baby son now, so it is likely that the armpit lump is just an inflammatory lesion. But given your family history, it may be prudent to see a doctor and also get an ultrasound of the breast and armpit done (a mammogram in a young lactating breast may be tricky to interpret).
All the Best, and God Bless!

The Content on this Site is presented in a summary fashion, and is intended to be used for educational and entertainment purposes only. It is not intended to be and should not be interpreted as medical advice or a diagnosis of any health or fitness problem, condition or disease; or a recommendation for a specific test, doctor, care provider, procedure, treatment plan, product, or course of action. Med Help International, Inc. is not a medical or healthcare provider and your use of this Site does not create a doctor / patient relationship. We disclaim all responsibility for the professional qualifications and licensing of, and services provided by, any physician or other health providers posting on or otherwise referred to on this Site and/or any Third Party Site. Never disregard the medical advice of your physician or health professional, or delay in seeking such advice, because of something you read on this Site. We offer this Site AS IS and without any warranties. By using this Site you agree to the following Terms and Conditions. If you think you may have a medical emergency, call your physician or 911 immediately.